The contribution of induction of temperate phages to the numbers of free somatic coliphages in waters is not significant

Somatic coliphages have been proposed as indicators of water quality. But several factors have been considered a drawback for their use as indicators. We evaluated the contribution of temperate phages to the numbers of somatic coliphages detected in water by ISO (International Standards Organization) standardised methods. Prophage induction from naturally occurring bacteria was assayed with mitomycin C, ciprofloxacin and UV irradiation. Results indicate that the presence of prophages will not influence the determinations of somatic coliphages in water.     

Mechanism of intramembrane proteolysis investigated with purified rhomboid proteases

Intramembrane proteases have the unusual property of cleaving peptide bonds within the lipid bilayer, an environment not obviously suited to a water-requiring hydrolysis reaction. These enzymes include site-2 protease, gamma-secretase/presenilin, signal peptide peptidase and the rhomboids, and they have a wide range of cellular functions. All have multiple transmembrane domains and, because of their high hydrophobicity, have been difficult to purify. We have now developed an in vitro assay to monitor rhomboid activity in the detergent solubilised state. This has allowed us to isolate for the first time a highly pure rhomboid with catalytic activity. Our results suggest that detergent-solubilised rhomboid activity mimics its activity in biological membranes in many aspects. Analysis of purified mutant proteins suggests that rhomboids use a serine protease catalytic dyad instead of the previously proposed triad. This analysis also suggests that other conserved residues participate in subsidiary functions like ligand binding and water supply. We identify a motif shared between rhomboids and the recently discovered derlins, which participate in translocation of misfolded membrane proteins.     

Elevated CO<Subscript>2</Subscript> reduces stomatal and metabolic limitations on photosynthesis caused by salinity in <Emphasis Type="Italic">Hordeum vulgare</Emphasis>

The future environment may be altered by high concentrations of salt in the soil and elevated [CO₂] in the atmosphere. These have opposite effects on photosynthesis. Generally, salt stress inhibits photosynthesis by stomatal and non-stomatal mechanisms; in contrast, elevated [CO₂] stimulates photosynthesis by increasing CO₂ availability in the Rubisco carboxylating site and by reducing photorespiration. However, few studies have focused on the interactive effects of these factors on photosynthesis. To elucidate this knowledge gap, we grew the barley plant, Hordeum vulgare (cv. Iranis), with and without salt stress at either ambient or elevated atmospheric [CO₂] (350 or 700 μmol mol⁻¹ CO₂, respectively). We measured growth, several photosynthetic and fluorescence parameters, and carbohydrate content. Under saline conditions, the photosynthetic rate decreased, mostly because of stomatal limitations. Increasing salinity progressively increased metabolic (photochemical and biochemical) limitation; this included an increase in non-photochemical quenching and a reduction in the PSII quantum yield. When salinity was combined with elevated CO₂, the rate of CO₂ diffusion to the carboxylating site increased, despite lower stomatal and internal conductance. The greater CO₂ availability increased the electron sink capacity, which alleviated the salt-induced metabolic limitations on the photosynthetic rate. Consequently, elevated CO₂ partially mitigated the saline effects on photosynthesis by maintaining favorable biochemistry and photochemistry in barley leaves.     

Shiga toxin-producing Escherichia coli O104:H4: a new challenge for microbiology

In 2011, Germany experienced the largest outbreak with a Shiga toxin-producing Escherichia coli (STEC) strain ever recorded. A series of environmental and trace-back and trace-forward investigations linked sprout consumption with the disease, but fecal-oral transmission was also documented. The genome sequences of the pathogen revealed a clonal outbreak with enteroaggregative E. coli (EAEC). Some EAEC virulence factors are carried on the virulence plasmid pAA. From an unknown source, the epidemic strains acquired a lambdoid prophage carrying the gene for the Shiga toxin. The resulting strains therefore possess two different mobile elements, a phage and a plasmid, contributing essential virulence genes. Shiga toxin is released by decaying bacteria in the gut, migrates through the intestinal barrier, and is transported via the blood to target organs, like the kidney. In a mouse model, probiotic bifidobacteria interfered with transport of the toxin through the gut mucosa. Researchers explored bacteriophages, bacteriocins, and low-molecular-weight inhibitors against STEC. Randomized controlled clinical trials of enterohemorrhagic E. coli (EHEC)-associated hemolytic uremic syndrome (HUS) patients found none of the interventions superior to supportive therapy alone. Antibodies against one subtype of Shiga toxin protected pigs against fatal neurological infection, while treatment with a toxin receptor decoy showed no effect in a clinical trial. Likewise, a monoclonal antibody directed against a complement protein led to mixed results. Plasma exchange and IgG immunoadsoprtion ameliorated the condition in small uncontrolled trials. The epidemic O104:H4 strains were resistant to all penicillins and cephalosporins but susceptible to carbapenems, which were recommended for treatment.     

Homogeneity of the Morphological Groups of Bacteriophages Infecting <Emphasis Type="Italic">Bacteroides fragilis</Emphasis> Strain HSP40 and Strain RYC2056

Bacteriophages infecting Bacteroides fragilis strains RYC2056 and HSP40 have been proposed as indicators of water quality. To accomplish this function, homogeneity of the group of phages detected by these strains is necessary to ensure that the final results are not due to the different kinetics of inactivation of the phages. To evaluate homogeneity, we observed by electron microscopy bacteriophages isolated from sewage with two Bacteroides fragilis strains (HSP40 and RYC2056). A predominant group of phages was observed, Siphoviridae with slightly curved tails. Detection of other minority groups, which could be present in the sample, was done with neutralization experiments by using antiserum against the majority group and with host mutants resistant to infection with the predominant phage. Although two other minority groups were observed, results showed that bacteriophages infecting B. fragilis strain HSP40 and strain RYC2056 form a homogeneous group, Siphoviridae with slightly curved tails being the most predominant in sewage. Received: 7 March 2002 / Accepted: 5 August 2002     

Method for Isolation of Bacteroides Bacteriophage Host Strains Suitable for Tracking Sources of Fecal Pollution in Water

Bacteriophages infecting Bacteroides are potentially a good tool for fecal source tracking, but different Bacteroides host strains are needed for different geographic areas. A feasible method for isolating Bacteroides host strains for phages present in human fecal material is described. Useful strains were identified for application in Spain and the United Kingdom. One strain, GA-17, identified as Bacteroides thetaiotaomicron, was tested in several locations in Europe with excellent performance in Southern Europe.     

Marine sponges (Porifera) from the Bahía San Antonio (North Patagonian Gulfs,Argentina), with additions to the phylogeography of the widely distributed Cliona aff. celata and Hymeniacidon perlevis,and the description of two new species

Six sponge species from Bahía San Antonio (north Argentinean Patagonia) are (re)described, including two new species, namely Halichondria (Halichondria) elenae sp. nov. and Clathria (Microciona) saoensis sp. nov., and three new records for the Argentinean coast. Halichondria (H.) elenae sp. nov. is the only yellowish-greenish SW Atlantic Halichondria with oxeas up to 450?µm. The new species’ 18S rRNA blasted with Halichondria bowerbanki from Ireland, but it is argued that co-specificity is unlikely, in view of their rather distinct morphologies. Clathria (M.) saoensis sp. nov. is the only C. (Microciona) in the SW Atlantic, SE Pacific, and (sub)Antarctic regions with smooth (or nearly so) principal megascleres, mostly below 500?µm long, as well as moderately curved toxas, and isochelae of regular non-cleistochelate shape. Cliona aff. celata and Hymeniacidon perlevis had their identifications confirmed by the sequencing of their 28S and 18S rRNA genes, respectively, and mitochondrial CO1. Both of them clustered with previously sequenced specimens from the Temperate North Atlantic, apart from additional samples from SE Brazil, in the case of C. aff. celata, and China and South Korea, in the case of H. perlevis.